Methods and apparatuses for random access procedure in medium access control layer

ABSTRACT

A method performed by a UE for implementing a random access procedure is provided. The method transmits a MSGA, monitoring an MSGB-RNTI within an MSGB time window starting from an earliest symbol of an earliest PDCCH occasion after the MSGA transmission. The method receives the MSGB in a first slot. The MSGB includes a success RAR that contains a HARQ Feedback Timing Indicator, a Physical Uplink Control Channel (PUCCH) Resource Indicator, and a UE Contention Resolution Identity. The method determines, by a MAC entity of the UE, to instruct a lower layer to transmit a HARQ feedback in a second slot in response to the reception of the success RAR. The method delivers, by the MAC entity, the HARQ Feedback Timing Indicator and the PUCCH Resource Indicator to the lower layer, and performs, by the lower layer, a HARQ feedback delivery on an uplink (UL) resource.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation application of U.S. patentapplication Ser. No. 17/091,626, filed on Nov. 6, 2020, which claims thebenefit of and priority to U.S. Provisional Patent Application Ser. No.62/932,187, filed on Nov. 7, 2019. The contents of all above-identifiedapplications are hereby incorporated herein fully by reference for allpurposes.

FIELD

The present disclosure generally relates to wireless communications, andmore specifically, relates to methods and apparatuses for two-steprandom access procedure in the Medium Access Control (MAC) Layer.

BACKGROUND

With the tremendous growth in the number of connected devices and therapid increase in user/network traffic volume, various efforts have beenmade to improve different aspects of wireless communication for thenext-generation wireless communication system, such as thefifth-generation (5G) New Radio (NR), by improving data rate, latency,reliability, and mobility.

The 5G NR system is designed to provide flexibility and configurabilityto optimize the network services and types, accommodating various usecases such as enhanced Mobile Broadband (eMBB), massive Machine-TypeCommunication (mMTC), and Ultra-Reliable and Low-Latency Communication(URLLC).

However, as the demand for radio access continues to increase, there isa need for further improvements in wireless communication for thenext-generation wireless communication system.

SUMMARY

The present disclosure is directed to methods and apparatuses fortwo-step random access procedure in the MAC Layer.

According to a first aspect of the present disclosure, a methodperformed by a User Equipment (UE) for a 2-step random access (RA)procedure including a message A (MSGA) and a message B (MSGB) isprovided. The method includes: transmitting the MSGA of the 2-steprandom access procedure; monitoring a MSGB-Radio Network TemporaryIdentity (RNTI) within a MSGB window, the MSGB window starting from anearliest symbol of an earliest Physical Downlink Control Channel (PDCCH)occasion after an end of the MSGA transmission; receiving, in responseto the MSGA, the MSGB in a first slot, the MSGB including a successrandom access response (RAR), the success RAR containing a HybridAutomatic Repeat reQuest (HARQ) Feedback Timing Indicator, a PhysicalUplink Control Channel (PUCCH) Resource Indicator, and a UE ContentionResolution Identity; determining, by a Media Access Control (MAC) entityof the UE, to instruct a lower layer to transmit a HARQ feedback in asecond slot in response to the reception of the success RAR, the secondslot indicated by the HARQ Feedback Timing Indicator; delivering, by theMAC entity of the UE, the HARQ Feedback Timing Indicator and the PUCCHResource Indicator to the lower layer; and performing, by the lowerlayer, a HARQ feedback delivery on an uplink (UL) resource within thesecond slot determined by the HARQ Feedback Timing Indicator and thePUCCH Resource Indicator.

In an implementation of the first aspect, the MSG A contains a CommonControl Channel (CCCH) MAC Service Data Unit (SDU).

In another implementation of the first aspect, the HARQ feedback istransmitted when the UE Contention Resolution Identity in a MACsub-Packet Data Unit (PDU) of the success RAR matches the CCCH MAC SDU.

In yet another implementation of the first aspect, the HARQ feedback istransmitted on an UL bandwidth part (BWP).

In yet another implementation of the first aspect, the UL resourcecorresponds to one of a list of PUCCH resource candidates indicated bythe PUCCH Resource Indicator.

In yet another implementation of the first aspect, the list of PUCCHresource candidates is preconfigured by a radio resource control (RRC)configuration, the list of PUCCH resource candidates being associatedwith the UL BWP.

In yet another implementation of the first aspect, the second slot isseparated from the first slot by a slot offset in a time domain, and theslot offset is indicated by the HARQ Feedback Timing Indicator.

In yet another implementation of the first aspect, the lower layer is aphysical (PHY) layer of the UE.

According to a second aspect of the present disclosure, a user equipment(UE) configured to perform a 2-step random access (RA) procedureincluding a message A (MSGA) and a message B (MS GB) is provided. The UEincludes one or more non-transitory computer-readable media havingcomputer-executable instructions embodied thereon, and at least oneprocessor coupled to the one or more non-transitory computer-readablemedia, and configured to execute the computer-executable instructionsto: transmit, by transmit circuitry, the MSGA of the 2-step randomaccess procedure; monitor a MSGB-Radio Network Temporary Identity (RNTI)within a MSGB window, the MSGB window starting from an earliest symbolof an earliest Physical Downlink Control Channel (PDCCH) occasion afteran end of the MSGA transmission; receive, by reception circuitry, theMSGB in a first slot in response to the MSGA, the MSGB including asuccess random access response (RAR), the success RAR containing aHybrid Automatic Repeat reQuest (HARQ) Feedback Timing Indicator, aPhysical Uplink Control Channel (PUCCH) Resource Indicator, and a UEContention Resolution Identity; determine, by a Media Access Control(MAC) entity, to instruct a lower layer to transmit a HARQ feedback in asecond slot in response to the reception of the success RAR, the secondslot indicated by the HARQ Feedback Timing Indicator; deliver, by theMAC entity of the UE, the HARQ Feedback Timing Indicator and the PUCCHResource Indicator to the lower layer; and perform, by the lower layer,a HARQ feedback delivery on an uplink (UL) resource within the secondslot determined by the HARQ Feedback Timing Indicator and the PUCCHResource Indicator.

In an implementation of the second aspect, the MSG A contains a CommonControl Channel (CCCH) MAC Service Data Unit (SDU).

In another implementation of the second aspect, the HARQ feedback istransmitted when the UE Contention Resolution Identity in a MACsub-Packet Data Unit (PDU) of the success RAR matches the CCCH MAC SDU.

In yet another implementation of the second aspect, the HARQ feedback istransmitted on an UL bandwidth part (BWP).

In yet another implementation of the second aspect, the UL resourcecorresponds to one of a list of PUCCH resource candidates indicated bythe PUCCH Resource Indicator.

In yet another implementation of the second aspect, the list of PUCCHresource candidates is preconfigured by a radio resource control (RRC)configuration, the list of PUCCH resource candidates being associatedwith the UL BWP.

In yet another implementation of the second aspect, the second slot isseparated from the first slot by a slot offset in a time domain, and theslot offset is indicated by the HARQ Feedback Timing Indicator.

In yet another implementation of the second aspect, the lower layer is aphysical (PHY) layer of the UE.

According to a third aspect of the present disclosure, a methodperformed by a User Equipment (UE) for a 2-step random access (RA)procedure including a message A (MSGA) and a message B (MSGB) isprovided. The method includes: transmitting the MSGA of the 2-step RAprocedure, the MSGA including a Common Control Channel (CCCH) MediaAccess Control (MAC) Service Data Unit (SDU); monitoring an MSGB-RadioNetwork Temporary Identity (RNTI) within an MSGB time window, the MSGBtime window starting from an earliest symbol of an earliest PhysicalDownlink Control Channel (PDCCH) occasion after an end of the MSGAtransmission; receiving, in response to the MSGA, the MSGB in a firstslot, the MSGB including a success random access response (RAR), thesuccess RAR containing a Hybrid Automatic Repeat reQuest (HARQ) FeedbackTiming Indicator, a Physical Uplink Control Channel (PUCCH) ResourceIndicator, and a UE Contention Resolution Identity; determining, by aMAC entity of the UE, to instruct a lower layer to transmit a HARQfeedback in response to the reception of the success RAR, wherein theHARQ feedback is transmitted in a second slot determined by the HARQFeedback Timing Indicator, and wherein the second slot is separated fromthe first slot by an offset, the offset including a timing offset valuedetermined from a list of PUCCH resource offset candidates; delivering,by the MAC entity of the UE, the HARQ Feedback Timing Indicator and thePUCCH Resource Indicator to the lower layer; and transmitting, by thelower layer, the HARQ feedback on an uplink (UL) resource within thesecond slot in response to the UE Contention Resolution Identity in aMAC sub-Protocol Data Unit (subPDU) of the success RAR matching the CCCHMAC SDU, wherein the UL resource is determined by the PUCCH ResourceIndicator and the UL resource corresponding to one of the list of PUCCHresource candidates indicated by the PUCCH Resource Indicator, andwherein the list of PUCCH resource candidates is associated with a ULbandwidth part (BWP).

In an implementation of the third aspect, the HARQ feedback istransmitted on the UL BWP.

In another implementation of the third aspect, the list of PUCCHresource candidates is preconfigured by a radio resource control (RRC)configuration.

In yet another implementation of the third aspect, the lower layerincludes a physical (PHY) layer of the UE.

According to a fourth aspect of the present disclosure, a user equipment(UE) configured to perform a 2-step random access (RA) procedureincluding a message A (MSGA) and a message B (MS GB) is provided. The UEincludes one or more non-transitory computer-readable media havingcomputer-executable instructions embodied thereon, and at least oneprocessor coupled to the one or more non-transitory computer-readablemedia, and configured to execute the computer-executable instructions tocause the UE to: transmit the MSGA of the 2-step RA procedure, the MSGAincluding a Common Control Channel (CCCH) Media Access Control (MAC)Service Data Unit (SDU); monitor an MSGB-Radio Network TemporaryIdentity (RNTI) within an MSGB time window, the MSGB time windowstarting from an earliest symbol of an earliest Physical DownlinkControl Channel (PDCCH) occasion after an end of the MSGA transmission;receive, in response to the MSGA, the MSGB in a first slot, the MSGBincluding a success random access response (RAR), the success RARcontaining a Hybrid Automatic Repeat reQuest (HARQ) Feedback TimingIndicator, a Physical Uplink Control Channel (PUCCH) Resource Indicator,and a UE Contention Resolution Identity; determine, by a MAC entity ofthe UE, to instruct a lower layer to transmit a HARQ feedback inresponse to the reception of the success RAR, wherein the HARQ feedbackis transmitted in a second slot determined by the HARQ Feedback TimingIndicator, and wherein the second slot is separated from the first slotby an offset, the offset including a timing offset value determined froma list of PUCCH resource offset candidates; deliver, by the MAC entityof the UE, the HARQ Feedback Timing Indicator and the PUCCH ResourceIndicator to the lower layer; and transmit, by the lower layer, the HARQfeedback on an uplink (UL) resource within the second slot, the ULresource being determined by the PUCCH Resource Indicator when the UEContention Resolution Identity in a MAC sub-Protocol Data Unit (subPDU)of the success RAR matches the CCCH MAC SDU, the UL resourcecorresponding to one of the list of PUCCH resource candidates indicatedby the PUCCH Resource Indicator, wherein the list of PUCCH resourcecandidates is associated with a UL bandwidth part (BWP).

In an implementation of the fourth aspect, the HARQ feedback istransmitted on the UL BWP.

In another implementation of the fourth aspect, the list of PUCCHresource candidates is preconfigured by a radio resource control (RRC)configuration.

In yet another implementation of the fourth aspect, the lower layercomprises a physical (PHY) layer of the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed disclosure when read with the accompanying figures. Variousfeatures are not drawn to scale. Dimensions of various features may bearbitrarily increased or reduced for clarity of discussion.

FIG. 1A illustrates a 4-step CBRA procedure, in accordance with anexample implantation of the present disclosure.

FIG. 1B illustrates a 2-step CBRA procedure, in accordance with anexample implantation of the present disclosure.

FIG. 1C illustrates a CFRA procedure, in accordance with an exampleimplantation of the present disclosure.

FIG. 1D illustrates a fallback from a 2-step RA to a 4-step RAprocedure, in accordance with an example implantation of the presentdisclosure.

FIG. 2 illustrates a flowchart of a method by a UE for a random accessprocedure where both 2-step and 4-step RA random access resources areconfigured by a base station, according to an example implementation ofthe present application.

FIG. 3 illustrates a schematic diagram of a payload of a MSGAtransmission on a PUSCH having a C-RNTI MAC CE, in accordance with anexample implementation of the present disclosure.

FIG. 4 illustrates a schematic diagram of a payload of a MSGAtransmission on a PUSCH having a MAC SDU from a CCCH, in accordance withan example implementation of the present disclosure.

FIG. 5 illustrates a schematic diagram of MSGB reception while a payloadof a MSGA transmission on a PUSCH includes a MAC SDU from a CCCH, inaccordance with an example implementation of the present disclosure.

FIG. 6 illustrates a schematic diagram of MSGB reception while a payloadof a MSGA transmission on a PUSCH includes a C-RNTI MAC CE, inaccordance with an example implementation of the present disclosure.

FIG. 7 illustrates a flowchart of a method by a UE for performing aspecific HARQ process for a transport block received in a MSGB, inaccordance with an example implementation of the present disclosure.

FIG. 8 illustrates a flowchart of a method by a UE for a DL HARQprocess, in accordance with an example implementation of the presentdisclosure.

FIG. 9 illustrates a schematic diagram of slot offsets K0 and K1, inaccordance with an example implementation of the present disclosure.

FIG. 10 illustrates a schematic diagram of MSGB reception on a PDSCHindicated by DCI with CRC bits scrambled by an MSGB-RNTI transmitted ona PDCCH, in accordance with an example implementation of the presentdisclosure.

FIG. 11 illustrates a flowchart of a method by a UE for a DL HARQprocess, in accordance with an example implementation of the presentdisclosure.

FIG. 12 illustrates a flowchart of another method by a UE for a DL HARQprocess, in accordance with an example implementation of the presentdisclosure.

FIG. 13 illustrates a block diagram of a node for wirelesscommunication, in accordance with various aspects of the presentdisclosure.

DESCRIPTION

The following contains specific information pertaining to exampleimplementations in the present disclosure. The drawings and theiraccompanying detailed disclosure are directed to merely exampleimplementations of the present disclosure. However, the presentdisclosure is not limited to merely these example implementations. Othervariations and implementations of the present disclosure will occur tothose skilled in the art. Unless noted otherwise, like or correspondingelements among the figures may be indicated by like or correspondingreference numerals. Moreover, the drawings and illustrations in thepresent disclosure are generally not to scale and are not intended tocorrespond to actual relative dimensions.

For consistency and ease of understanding, like features are identified(although, in some examples, not illustrated) by numerals in the examplefigures. However, the features in different implementations may differin other respects, and thus shall not be narrowly confined to what isillustrated in the figures.

References to “one implementation,” “an implementation,” “exampleimplementation,” “various implementations,” “some implementations,”“implementations of the present disclosure,” etc., may indicate that theimplementation(s) of the present disclosure may include a particularfeature, structure, or characteristic, but not every possibleimplementation of the present disclosure necessarily includes theparticular feature, structure, or characteristic. Further, repeated useof the phrase “in one implementation,” “in an example implementation,”or “an implementation,” do not necessarily refer to the sameimplementation, although they may. Moreover, any use of phrases like“implementations” in connection with “the present disclosure” are nevermeant to characterize that all implementations of the present disclosuremust include the particular feature, structure, or characteristic, andshould instead be understood to mean “at least some implementations ofthe present disclosure” includes the stated particular feature,structure, or characteristic. The term “coupled” is defined asconnected, whether directly or indirectly through interveningcomponents, and is not necessarily limited to physical connections. Theterm “comprising,” when utilized, means “including but not necessarilylimited to”; it specifically indicates open-ended inclusion ormembership in the disclosed combination, group, series, and theequivalent. The terms “system” and “network” in the present disclosuremay be used interchangeably.

The term “and/or” herein is only an association relationship fordescribing associated objects and represents that three relationshipsmay exist, for example, A and/or B may represent that: A exists alone, Aand B exist at the same time, and B exists alone. “A and/or B and/or C”may represent that at least one of A, B, and C exists. The character “/”used herein generally represents that the former and latter associatedobjects are in an “or” relationship.

Additionally, for a non-limiting explanation, specific details, such asfunctional entities, techniques, protocols, standards, and the like, areset forth for providing an understanding of the disclosed technology. Inother examples, detailed disclosure of well-known methods, technologies,systems, architectures, and the like are omitted so as not to obscurethe present disclosure with unnecessary details.

The terms mentioned in the present disclosure are defined as follows.Unless otherwise specified, the terms in the present disclosure have thefollowing meanings.

Abbreviation Full name 3GPP 3rd Generation Partnership Project 5G 5thgeneration ACK Acknowledge AS Access Stratum BA Bandwidth Adaptation BFBeam Failure BFD Beam Failure Detection BFI Beam Failure Instance BFRBeam Failure Recovery BFRQ Beam Failure Recovery Request BFRR BeamFailure Recovery Response BS Base Station BSR Buffer Status Report BWPBand Width Part CA Carrier Aggregation CC Component Carriers CE ControlElement CG Cell Group CSI Channel State Information CSI-RS Channel StateInformation based Reference Signal CQI Channel Quality Indicator C-RNTICell Radio Network Temporary Identifier CS-RNTI Configured SchedulingRadio Network Temporary Identifier DRB Data Radio Bearer DTCH DedicatedTraffic Channel DL Downlink DCI Downlink Control Information DL-SCHDownlink Shared Channel DRX Discontinuous Reception EN-DC E-UTRA NR DualConnect ID Identity L1 Layer 1 L2 Layer 2 LCH Logical Channel LCIDLogical Channel Identity LTE Long Term Evolution MAC Medium AccessControl MAC CE MAC Control Element MCG Master Cell Group MIMOMulti-input Multi-output MSC-C-RNTI Modulation Coding Scheme Cell RadioNetwork Temporary Identifier Msg Message MSGA Message A MSGB Message BMSGB-RNTI Message B Radio Network Temporary Identifier NACK NegativeAcknowledge NBI New Beam Identification NDI New Data Indicator NR NewRAT/Radio NW Network PCell Primary Cell PDCCH Physical Downlink ControlChannel PDSCH Physical Downlink Shared Channel PDCP Packet DataConvergence Protocol PDU Protocol Data Unit PHY Layer Physical LayerPRACH Physical Random Access Channel PSCell Primary SCell PUCCH PhysicalUplink Control Channel PUSCH Physical Uplink Shared Channel QoS Qualityof Service RA Random Access RACH Random Access Channel RAR Random AccessResponse RF Radio Frequency RNTI Radio Network Temporary Identifier RRCRadio Resource Control RS Reference Signal RSRP Reference SignalReceived Power Rx Reception SCell Secondary Cell SCG Secondary CellGroup SDAP Service Data Adaptation Protocol SDU Service Data Unit SINRSignal-to-Noise and Interference Ratio SR Scheduling Request SRSSounding Reference Signal SSB Synchronization Signal Block SpCellSpecial Cell SLIV Start and Length Indicator Value SUL Supplementary ULTAG Timing Advance Group TB Transport Block TRP Transmission/ReceptionPoint TS Technical Specification Tx Transmission UCI Uplink ControlInformation UE User Equipment UL Uplink UL-SCH Uplink Shared Channel

Persons skilled in the art will immediately recognize that any disclosednetwork function(s) or algorithm(s) may be implemented by hardware,software, or a combination of software and hardware. Disclosed functionsmay correspond to modules that may be software, hardware, firmware, orany combination thereof. The software implementation may comprisecomputer-executable instructions stored on a computer-readable mediumsuch as memory or other types of storage devices. For example, one ormore microprocessors or general-purpose computers with communicationprocessing capability may be programmed with corresponding executableinstructions and carry out the disclosed network function(s) oralgorithm(s). The microprocessors or general-purpose computers may beformed of Applications Specific Integrated Circuitry (ASIC),programmable logic arrays, and/or using one or more Digital SignalProcessors (DSPs). Although some of the example implementationsdisclosed are oriented to software installed and executing on computerhardware, alternative example implementations implemented as firmware oras hardware or combination of hardware and software are well within thescope of the present disclosure.

The computer-readable medium may include, but is not limited to, RandomAccess Memory (RAM), Read-Only Memory (ROM), Erasable ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM), flash memory, Compact Disc Read-Only Memory (CD-ROM),magnetic cassettes, magnetic tape, magnetic disk storage, or any otherequivalent medium capable of storing computer-readable instructions.

A radio communication network architecture (e.g., a Long-Term Evolution(LTE) system, an LTE-Advanced (LTE-A) system, or an LTE-Advanced Prosystem) may typically include at least one Base Station (BS), at leastone UE, and one or more optional network elements that provideconnection towards a network. The UE may communicate with the network(e.g., a Core Network (CN), an Evolved Packet Core (EPC) network, anEvolved Universal Terrestrial Radio Access Network (E-UTRAN), aNext-Generation Core (NGC), or an Internet), through a Radio AccessNetwork (RAN) established by the BS.

In the present disclosure, a UE may include, but is not limited to, amobile station, a mobile terminal or device, a user communication radioterminal. For example, a UE may be a portable radio equipment, whichincludes, but is not limited to, a mobile phone, a tablet, a wearabledevice, a sensor, or a Personal Digital Assistant (PDA) with wirelesscommunication capability. The UE may be configured to receive andtransmit signals over an air interface to one or more cells in a RAN.

A BS may include, but is not limited to, a Node B (NB) as in theUniversal Mobile Telecommunication System (UMTS), an evolved Node B(eNB) as in the LTE-A, a Radio Network Controller (RNC) as in the UNITS,a Base Station Controller (BSC) as in the Global System for Mobilecommunications (GSM)/GSM Enhanced Data rates for GSM Evolution (EDGE)Radio Access Network (GERAN), a next-generation eNB (ng-eNB) as in anEvolved Universal Terrestrial Radio Access (E-UTRA) BS in connectionwith the 5GC, a next-generation Node B (gNB) as in the 5G Access Network(5G-AN), and any other apparatus capable of controlling radiocommunication and managing radio resources within a cell. The BS mayconnect to serve the one or more UEs through a radio interface to thenetwork.

A BS may be configured to provide communication services according to atleast one of the following Radio Access Technologies (RATs): WorldwideInteroperability for Microwave Access (WiMAX), GSM (often referred to as2G), GERAN, General Packet Radio Service (GPRS), UNITS (often referredto as 3G) based on basic Wideband-Code Division Multiple Access(W-CDMA), High-Speed Packet Access (HSPA), LTE, LTE-A, enhanced L(eLTE), NR (often referred to as 5G), and LTE-A Pro. However, the scopeof the present disclosure should not be limited to the protocolsmentioned above.

The BS may be operable to provide radio coverage to a specificgeographical area using a plurality of cells included in the RAN. The BSmay support the operations of the cells. Each cell may be operable toprovide services to at least one UE within its radio coverage. Morespecifically, each cell (often referred to as a serving cell) mayprovide services to serve one or more UEs within its radio coverage(e.g., each cell schedules the Downlink (DL) and optionally Uplink (UL)resources to at least one UE within its radio coverage for DL andoptionally UL packet transmissions). The BS may communicate with one ormore UEs in the radio communication system through the plurality ofcells. A cell may allocate Sidelink (SL) resources for supportingProximity Service (ProSe), LTE SL services, and LTE/NRVehicle-to-Everything (V2X) services. Each cell may have overlappedcoverage areas with other cells. In Multi-RAT Dual Connectivity (MR-DC)cases, the primary cell of an MCG or a SCG may be referred to as aSpecial Cell (SpCell). A PCell may refer to the SpCell of an MCG. APrimary SCG Cell (PSCell) may refer to the SpCell of an SCG. MCG mayrefer to a group of serving cells associated with the Master Node (MN),including the SpCell and optionally one or more SCells. An SCG may referto a group of serving cells associated with the Secondary Node (SN),including the SpCell and optionally one or more SCells.

As discussed above, the frame structure for NR is to support flexibleconfigurations for accommodating various next-generation (e.g., 5G)communication requirements, such as eMBB, mMTC, and URLLC, whilefulfilling high reliability, high data rate, and low latencyrequirements. The orthogonal frequency-division multiplexing (OFDM)technology, as agreed in the 3GPP, may serve as a baseline for an NRwaveform. The scalable OFDM numerology, such as the adaptive sub-carrierspacing, the channel bandwidth, and the cyclic prefix (CP), may also beused. Additionally, two coding schemes are considered for NR: (1)low-density parity-check (LDPC) code and (2) polar code. The codingscheme adaption may be configured based on the channel conditions and/orthe service applications.

Moreover, it is also considered that in a transmission time interval ofa single NR frame, at least DL transmission data, a guard period, and ULtransmission data should be included, where the respective portions ofthe DL transmission data, the guard period, the UL transmission datashould also be configurable, for example, based on the network dynamicsof NR. Besides, an SL resource may also be provided in an NR frame tosupport ProSe services.

In various implementations of the present disclosure, a cell may be aradio network object that can be uniquely identified by a User Equipmentfrom a (cell) identification that is broadcast over a geographical areafrom one UTRAN Access Point. A Cell is either FDD or TDD mode.

In various implementations of the present disclosure, for a UE inRRC_CONNECTED not configured with CA/DC, there is only one serving cellcomprising of the primary cell. For a UE in RRC_CONNECTED configuredwith CA/DC the term ‘serving cells’ is used to denote the set of cellscomprising of the Special Cell(s) and all secondary cells.

In various implementations of the present disclosure, in CarrierAggregation (CA), two or more Component Carriers (CCs) are aggregated. AUE may simultaneously receive or transmit on one or multiple CCsdepending on its capabilities. CA is supported for both contiguous andnon-contiguous CCs. When CA is deployed frame timing and SFN are alignedacross cells that can be aggregated. The maximum number of configuredCCs for a UE is 16 for DL and 16 for UL. When CA is configured, the UEonly has one RRC connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell provides theNAS mobility information, and at RRC connectionre-establishment/handover, one serving cell provides the security input.This cell is referred to as the Primary Cell (PCell). Depending on UEcapabilities, Secondary Cells (SCells) can be configured to formtogether with the PCell a set of serving cells. The configured set ofserving cells for a UE therefore always consists of one PCell and one ormore SCells.

In various implementations of the present disclosure, a HARQ is afunctionality that ensures delivery between peer entities at Layer 1(i.e., Physical Layer). A single HARQ process supports one TransportBlock (TB) when the physical layer is not configured for downlink/uplinkspatial multiplexing, and when the physical layer is configured fordownlink/uplink spatial multiplexing, a single HARQ process supports oneor multiple TBs. There is one HARQ entity per serving cell. Each of HARQentity supports a parallel (number) of DL and UL HARQ process.

In various implementations of the present disclosure, a HARQ-ACKinformation bit value of 0 represents a negative acknowledgement (NACK)while a HARQ-ACK information bit value of 1 represents a positiveacknowledgement (ACK).

In various implementations of the present disclosure, the MAC entity cansetup one or more timers for different purposes, for example, fortriggering uplink signaling retransmission or limiting some uplinksignaling retransmission period. A timer is running once it is started,until it is stopped or until it expires; otherwise it is not running. Atimer can be started if it is not running or restarted if it is running.A timer is always started or restarted from its initial value, where theinitial value can be (but is not limited to) configured by the basestation via downlink RRC signaling.

In various implementations of the present disclosure, a subset of thetotal cell bandwidth of a cell is referred to as a BWP and BA isachieved by configuring the UE with BWP(s) and telling the UE which ofthe configured BWPs is currently the active one. To enable BA on thePCell, the base station configures the UE with UL and DL BWP(s). Toenable BA on SCells in case of CA, the base station configures the UEwith DL BWP(s) at least (i.e. there may be none in the UL). For thePCell, the initial BWP is the BWP used for initial access. For theSCell(s), the initial BWP is the BWP configured for the UE to firstoperate at SCell activation. UE may be configured with a first activeuplink BWP by a firstActiveUplinkBWP IE. If the first active uplink BWPis configured for an SpCell, the firstActiveUplinkBWP IE field containsthe ID of the UL BWP to be activated upon performing the RRC(re-)configuration. If the field is absent, the RRC (re-)configurationdoes not impose a BWP switch. If the first active uplink BWP isconfigured for an SCell, the firstActiveUplinkBWP IE field contains theID of the uplink bandwidth part to be used upon MAC-activation of anSCell.

In various implementations of the present disclosure, for DLtransmission, the base station can dynamically allocate resources to UEsvia the C-RNTI/MCS-C-RNTI/CS-RNTI on PDCCH(s). A UE always monitors thePDCCH(s) in order to find possible assignments when its downlinkreception is enabled (activity governed by DRX when configured). When CAis configured, the same C-RNTI applies to all serving cells.

In various implementations of the present disclosure, PDCCH(s) can beused to schedule DL transmissions on PDSCH(s) and UL transmissions onPUSCH(s).

In various implementations of the present disclosure, for a TimeAlignment Timer, RRC configures the initial value of the timer. Thetimer is for the maintenance of UL time alignment. Wherein thetimeAlignmentTimer is per timing advance group maintained. The timercontrols how long the MAC entity considers the Serving Cells belongingto the associated TAG to be uplink time aligned.

In various implementations of the present disclosure, a Start and LengthIndicator Value (SLIV) is used for the time domain allocation forPUSCH(s)/PDSCH(s). It defines the start symbol and the number ofconsecutive symbols for the PUSCH/PDSCH allocation.

In various implementations of the present disclosure, data from theupper layer (e.g., the MAC layer) given to the physical layer isbasically referred as transport block.

It should be understood that the terms, definitions and abbreviationsdisclosed in the present disclosure are either imported from existingdocumentation (ETSI, ITU or elsewhere) or newly created by 3GPP expertswhenever a need for precise vocabulary was identified.

I. Types of Random Access Procedure

In the 3rd Generation Partnership Project (3GPP) next generationcellular wireless communication system (e.g., a 5^(th) Generation (5G)New Radio wireless communication system), the following types of randomaccess procedures will be supported: a 4-step contention based randomaccess (CBRA) procedure, a 2-step CBRA procedure, and a contention freerandom access (CFRA) procedure.

FIG. 1A illustrates a 4-step CBRA procedure, in accordance with anexample implantation of the present disclosure. As illustrated in FIG.1A, diagram 100A includes a UE 110 and a base station (e.g., a gNB) 120.As shown in FIG. 1A, the 4-step contention-based random access proceduremay start by the UE 110 sending, in action 102, a Random Access Preamble(Msg1) to the base station 120. The UE 110 may send the RA preamble tothe base station 120 on a Physical Random Access Channel (PRACH) in theuplink. In response, in action 104, the base station 120 may send aRandom Access Response (RAR) (Msg2) to the UE 110. The RAR may begenerated by a MAC entity and transmitted on a Downlink Shared Channel(DL-SCH). The RAR, transmitted in action 104 may include an RA-preambleidentifier, Timing Alignment information for the primary Timing AdvancedGroup (pTAG), initial UL grant, and assignment of Temporary Cell-RadioNetwork Temporary Identity (C-RNTI). After receiving the RAR, the UE 110may send, in action 106, a first scheduled UL transmission (Msg3), forexample, on an Uplink Shared Channel (UL-SCH) to the base station 120.After the base station 120 receives the first scheduled UL transmission,the base station may send, in action 108, a Contention Resolutionmessage (Msg4) to the UE 110 on the DL.

In an RA procedure, upon receiving a RAR or Msg2 (e.g., in action 104),if the RAR contains a MAC sub-Protocol Data Unit (subPDU) with an RApreamble identifier that is associated with the transmitted preamble(e.g., when the identifier matches the preamble's index), the RARreception may be considered as successful. That is, a RAR, which is aMAC PDU, may include one or more MAC subPDUs. A MAC subPDU may have asubheader part and a payload part. In some of the presentimplementations, the MAC subheader in the RAR may include an RA preambleidentifier (e.g., RAPID) that is associated with the RA preamble index.That is, the RA preamble identifier may match the preamble indexassociated with the preamble for the UE to determine that the receivedRAR is associated with the sent preamble.

After the UE determines that the RAR reception is successful, the MAClayer (e.g., in the UE) may indicate the received UL grant to the lowerlayers to transmit the Msg3 (e.g., in action 106). Once the Msg3 istransmitted, the MAC entity may start a timer (e.g., thera-ContentionResolutionTimer) and restart the timer (e.g., thera-ContentionResolutionTimer) at each Hybrid Automatic Repeat reQuest(HARQ) retransmission (e.g., in the first symbol after the end of theMsg3 transmission). An RA procedure may be considered as successfullycompleted when the contention resolution (e.g., in Msg4) is successfullyperformed in action 108. For example, when the UE Contention Resolutionidentity in the MAC Control Element (CE) matches the Common ControlChannel (CCCH) Service Data Unit (SDU) transmitted in the Msg3, or otherconditions defined in the 3GPP technical specification (e.g., TS 38.321)are met, then the contention resolution is considered successful.However, if the timer (e.g., the ra-ContentionResolutionTimer) expires,the contention resolution may be considered not successful if none ofthe successfully completed conditions (e.g., matching of the UEidentifiers, or other conditions defined in the 3GPP TS 38.321) issatisfied. The content of the 3GPP TS 38.321 is hereby incorporated byreference in its entirety.

FIG. 1B illustrates a 2-step CBRA procedure, in accordance with anexample implantation of the present disclosure. As illustrated in FIG.1B, a diagram 100B includes a UE 110 and a base station (e.g., a gNB)120. As shown in FIG. 1B, the 2-step contention-based random accessprocedure may start by the UE 110 sending a MSGA to the base station 120in action 112.

As illustrated in FIG. 1B, in a 2-step CBRA procedure, the MSGA mayinclude a preamble on a PRACH and a payload on a PUSCH. Aftertransmitting MSGA, the UE may monitor for a response (e.g., a MSGB) fromthe network within a configured window. If a contention resolution issuccessful upon receiving the network response (e.g., the MSGB) inaction 114, the UE may end the random access procedure as illustrated inFIG. 1B.

FIG. 1C illustrates a contention free random access (CFRA) procedure, inaccordance with an example implantation of the present disclosure. Asillustrated in diagram 100C, the base station may transmit an RApreamble assignment (e.g., MSG0) in action 122. In action 124, the UE110 may transmit a random access preamble based on the RA preambleassignment received in action 122. In action 126, the base station 120may transmit a random access response (e.g., in MSG2).

FIG. 1D illustrates another CBRA procedure, in accordance with anexample implantation of the present disclosure.

As shown in FIG. 1D, the CBRA procedure may start by the UE 110 sendinga MSGA to the base station 120 in action 132. In the presentimplementation, a fallback indication is received in the MSGB in action134. Then, the UE 110 may perform a MSG3 (e.g., MSG3 in the 4-step RAprocedure) transmission in action 136, then monitor the contentionresolution (e.g., MSG 4 in the 4-step RA procedure) in action 138, asshown in FIG. 1D.

In the implementation shown in FIG. 1D, if contention resolution is notsuccessful after MSG3 (re)transmission(s), the UE may go back to MSGAtransmission. If the 2-step random access procedure is not successfullycompleted after a configured number of MSGA transmissions, UE may switchto the 4-step CBRA procedure (e.g., going back to MSG1).

For random access in a serving cell configured with SUL, the network canexplicitly signal which carrier to use (UL or SUL). Otherwise, the UEmay select an SUL carrier if and only if the measured quality of the DLis lower than a broadcast threshold. The UE may perform carrierselection before selecting between the 2-step and 4-step random accessprocedures. Once started, all uplink transmissions of the random accessprocedure remain on the selected carrier.

II. Random Access Procedure Operations

FIG. 2 illustrates a flowchart of a method by a UE for a random accessprocedure where both 2-step and 4-step RA random access resources areconfigured by a base station (e.g., a gNB), according to an exampleimplementation of the present application.

As illustrated in flowchart 200, in action 202, the UE receives RArelated configuration(s) from gNB via RACH-ConfigCommon,RACH-ConfigDedicated, RACH-ConfigGeneric, RA Prioritization and/or anyother information element (IE) which may be contained in broadcast RRCmessage and/or unicast RRC message.

The RA related configuration may include (but not limit to onlyinclude):

-   -   rsrp-ThresholdSSB-SUL: an RSRP threshold for the selection        between the NUL carrier and the SUL carrier;    -   rsrp-ThresholdSSB-2stepCBRA: an RSRP threshold for selection of        2-step random access;    -   msgATransMax: a maximum number of times a UE can transmit MSGA        transmission. The UE should fallback to 4-step random access        after msgATransMax times MSGA transmission;    -   msgB-Response Window: the time window to monitor MSGB (i.e., RA        response(s));    -   beamFailureRecoveryTimer_2StepRA: A Timer for beam failure        recovery timer. Upon expiration of the timer the UE does not use        CFRA for BFR. Value in millisecond (ms). Upon UE trigger a RA        for BFR and the UE select 2-step RA type, the UE starts the        timer.

In action 204, the UE performs (UL) carrier selection. The UE measuresthe pathloss of downlink reference signal which pre-configured toassociate with UL and SUL. The UE selects the SUL carrier for performingRandom Access procedure if the RSRP of the downlink pathloss referenceis less than the rsrp-ThresholdSSB-SUL. Otherwise, the UE selects normalUL carrier.

In action 206, the UE performs RA type selection/setting. The UE mayselect the 2-step RA if the rsrp-ThresholdSSB-2stepCBRA is configuredand the RSRP of downlink pathloss reference is above the configuredrsrp-ThresholdSSB-2stepCBRA. The UE may also select the 2-step RA if theBWP selected for random access procedure is only configured with 2-steprandom access resources. In the present implementation, it is assumedthat the UE selects the 2-step RA procedure. That is, the UE is toexecute the RA procedure staring from with the 2-step RA.

In action 208, the UE's RRC layer may configure the UE's MAC layer withRA related parameters for the RA procedure according to the RA relatedconfiguration(s) received in action 202.

In action 210, the UE may select RA resources associated with a SSB ifthe SSB with SS-RSRP above a rsrp-ThresholdSSB (as defined in 3GPP TS38.331) amongst the associated SSBs is available. It is noted that theRA resource selection may include a selection among CBRA resource andCFRA resource. In the present implementation, it is assumed that a CBRAresource is selected by the UE. That is, the UE is to perform the 4-stepCBRA.

In action 212, the UE may select an RA Preamble randomly with equalprobability from the 2-step Random Access Preambles associated with theselected SSB and perform corresponding preamble transmission by usingthe selected PRACH occasion as a first part of MSGA transmission.

In action 214, the UE may compute an MSGB-RNTI associated with the PRACHoccasion in which the RA Preamble is transmitted. As shown in FIG. 3 ,the MAC entity of the UE indicates to the Multiplexing and assembly(M&A) entity to include a C-RNTI MAC CE in the subsequent uplinktransmission (i.e., PUSCH transmission associated with the preambletransmission; the PUSCH resource is associated with the preamble and thePRACH occasion) if the PUSCH transmission is not being made for the CCCHlogical channel (for example, the RA is triggered for beam failurerecovery or the RA is triggered for RRC connection resume procedure).

On the other hand, as shown in FIG. 4 , the M&A entity may include theMAC SDU from CCCH (CCCH SDU) in the subsequent uplink transmission ifthe PUSCH transmission is made for the CCCH logical channel. Afterward,the MAC entity of the UE may instruct the physical layer to transmit thePUSCH using the corresponding MSGB-RNTI as second part of the MSGAtransmission (following action 212). That is, a TB for the PUSCHtransmission with CRC bits is to be scrambled by the MSGB-RNTI. Itshould be noted that, depending on how the UE computes a MSGB-RNTI, itis possible that different preambles selected by different UEs mayresult in the same MSGB-RNTI (i.e., the computation outcome of MSGB-RNTImay be same for multiple preambles). For example, there are two UEs(e.g., UE A and UE B) just trigger an RA, and both the UEs select toperform the 2-step RA. The two UEs, UE A and UE B, select preambles Aand B respectively. The UE A computes an MSGB-RNTI based on at least thetransmitted preamble A, and UE B computes an MSGB-RNTI based on at leastthe transmitted preamble B. The MSGB-RNTI of UE A may be the same as theMSGB-RNTI of UE B. Afterward, a base station (e.g., a gNB) may reply arandom access response to UE A and another random access response to UEB via a single MSGB transmission. That is, the base station maymultiplex a subPDU carrying RAR of UE A and a subPDU carrying RAR of UEB into a single MAC PDU. The MAC PDU is transmitted via a TB scheduledby a DL assignment (e.g., DCI) identified by the MSGB-RNTI (e.g., theDCI with cyclic redundancy check (CRC) bits scrambled by MSGB-RNTI).That is, both UEs will receive the TB and perform corresponding HARQdecoding. However, in a case the TB only contains the RAR of UE A anddoes not contain the RAR of UE B, the HARQ feedback of the received TBmay only need to be performed by the UE A. The HARQ feedbackdetermination may need the MAC entity's involvement.

In action 216, once the MSGA is transmitted, the UE may start amsgB-ResponseWindow (e.g., MSG B window). The MSGB window may startfrom, but is not limited to, the beginning of the earliest symbol (e.g.,first symbol) of the earliest upcoming PDCCH (e.g., first PDCCH) afterthe MSGA transmission. In another example, the MSGB window may startfrom, but is not limited to, the beginning of the earliest symbol (e.g.,first symbol) of upcoming PDCCH after the MSGA transmission plus atiming offset, where the timing offset may be, but is not limited to,pre-defined in the specification and pre-configured by the base stationon a per BWP/serving cell basis.

As shown in FIG. 5 , within the msgB-ResponseWindow, the UE monitors aPDCCH for a random access response identified by the MSGB-RNTI. On theother hand, in a case where the MSGA transmission with payload on aPUSCH includes a C-RNTI MAC CE, as shown in FIG. 6 , the UE monitors aPDCCH for a random access response identified by a C-RNTI within themsgB-ResponseWindow. In one example, in a case where the MSGAtransmission with payload on a PUSCH includes a C-RNTI MAC CE, as shownin FIG. 6 , the UE may additionally monitor a PDCCH for a random accessresponse identified by the MSGB-RNTI within the msgB-ResponseWindow.

In action 218, once a MSGB is received, the UE may perform contentionresolution according to one or more MAC subPDU contained in the MAC PDUof the MSGB. In a case where the MSGA transmission with payload on aPUSCH includes a C-RNTI MAC CE, the MSGB may either be indicated by adownlink assignment received on the PDCCH for the MSGB-RNTI or C-RNTI.On the other hand, in a case where the MSGA transmission with payload ona PUSCH includes a MAC SDU from a CCCH, the MSGB may be indicated by adownlink assignment received on the PDCCH for the MSGB-RNTI.

As an example shown in FIG. 5 , the MAC PDU of the MSGB may include, butis not limited to, several types of MAC subPDU: a MAC subPDU including abackoff indicator (BI), a MAC subPDU including a success RAR, a MACsubPDU including a fallback RAR, a MAC subPDU including data for a CCCH(data of a signal radio bearer) and a subPDU including padding (e.g., apadding subPDU). The detailed information carried by the subheaderand/or SDU of each type of subPDU is illustrated in FIG. 5 .

In one implementation, a subPDU including a success RAR may beidentified by, but is not limited to, a success RAR specific LCID or aspecific field (e.g., implicitly indicated via a pre-defined mappingrule) which is included in a subheader of the subPDU. For example, inthe subheader of the subPDU, a specific field set to “0” means that thecorresponding MAC SDU is a success RAR, and the specific field set to“1” means that the corresponding MAC SDU is a fallback RAR. Thesubheader may also include an L field that indicates the length of theMAC SDU or subPDU. The SDU of the subPDU may include a C-RNTI, UEcontention resolution ID timing advance information, and/or a newdefined timing advance command MAC CE. When a CCCH SDU is included inthe MSGA and the UE Contention Resolution Identity in the MAC subPDUmatches the CCCH SDU, the MAC entity of the UE may set the C-RNTI to thevalue received in the success RAR, and consider this Random AccessResponse reception successful and move to action s10. It should be notedthat, the subheader of the subPDU of a success RAR may include aspecific field which may be applied by the base station to indicate tothe UE (which tends to receive the success RAR for contentionresolution) whether the MSGB also include other subPDU the UE needs toreceive and/or decode. For example, a subPDU, which is located justafter the success RAR subPDU, may be indicated to be received by thespecific field. In another example, the specific field may be includedin the SDU of the success RAR subPDU.

In another implementation, a subPDU including a fallback RAR may beidentified by, but is not limited to, a fallback RAR specific LCID oridentified by a specific field (e.g., implicitly indicated via apre-defined mapping rule) which is included in a subheader of thesubPDU. For example, in a subheader of the subPDU, a specific field setto “0” means that the corresponding MAC SDU is a success RAR, and thespecific field set to “1” means that the corresponding MAC SDU is afallback RAR. The subheader may also include a Random Access PreambleIdentity (RAPID) field which indicates that the corresponding MAC SDU isassociated with a preamble transmission identified by the RAPID. Thesubheader may also include an L field that indicates the length of thesubPDU. The SDU of the subPDU may include a Temporary C-RNTI (e.g., aTC-RNTI as defined in 3GPP TS 38.321), a UL grant and a timing advancecommand. If the Random Access Preamble identifier in the MAC subPDUmatches the transmitted preamble, the MAC entity of the UE considersthis Random Access Response reception successful and moves to action230. And then, the UE perform Msg3 transmission based on the TC-RNTI andUL grant indicated by the fallback RAR.

In another example, if no success RAR or fallback RAR is received whichmatches (addressed for) the MSGA transmission within the MSGB window(e.g., no RAR is matched the transmitted MAGA or no RAR achievecontention resolution success), the UE performs random backoff accordingto the BI received in the MAC subPDU carrying a BI or a default BI, andthe flowchart goes back to action 210. In a case where a msgATransMax isconfigured by the base station, when the number of preambletransmissions reaches the msgATransMax and the UE fails in thecontention resolution (in action 218), the flowchart proceeds fromaction 218 to action action 224 to perform the 4-step RA procedure. TheBI value received from the MSGB may be released by the UE while fallbackfrom action 218 to action 224. In another example, the UE may set thebackoff window size to zero while falling back from action 218 to action224. In action 220, the MAC entity of the UE may consider the RAprocedure successfully completed.

It is noted that, actions 222, 224, 226, 228, 230, and 232 are similarto the legacy 4-step RA procedure defined in the 3GPP specifications(e.g., in 3GPP TS 38.321), the details of which are omitted for brevity.In action 218, if the UE fails in contention resolution, the UE may goback to action 210, if the corresponding Msg3 transmission in action 230is scheduled by the MSGB of action 216 from the 2-step RA procedure. Asshown in FIG. 2 , when the contention resolution is successful in eitheraction 218 or action 232, the flowchart 200 may proceeds to action 220where the RA procedure is complete.

It should be noted that not all the actions described above need to becompletely implemented. For example, only a subset of the actions may beimplemented by the UE. Also, the order in which the flowchart 200 may becarried out is not limited to the order shown in FIG. 2 .

III. HARQ Operation of MSGB Reception

As discussed above, in actions 216 and 218 in FIG. 2 and in theillustrations in FIGS. 5 and 6 , the UE may monitor a PDCCH for a randomaccess response identified by the MSGB-RNTI and/or C-RNTI, and performcontention resolution according to the MAC subPDU carried in a MAC PDUcarried by a MSGB. The MSGB is indicated by a DL assignment received ona PDCCH for either an MSGB-RNTI or a C-RNTI. The MSGB reception may behandled by (but is not limited to) a specific/dedicated DL HARQ processwhich means that the HARQ process for the MSGB is not dynamicallyindicated by the base station via a DCI on a PDCCH. The specific DL HARQprocess may be, but is not limited to, a DL HARQ process 0. In anotherexample, the specific DL HARQ process may be, but is not limited to, aHARQ process 0 of a DL serving cell that received the MSGB.

In a case where a MSGA transmission with payload on a PUSCH includes aMAC SDU from a CCCH, the corresponding MSGB may be indicated by a DLassignment received on the PDCCH for the MSGB-RNTI. After the receptionof the downlink assignment (which received on the PDCCH for theMSGB-RNTI), the UE may perform a specific HARQ process for the transportblock (TB) received in the MSGB as shown in FIG. 7 .

The specific HARQ process is different from a general DL HARQ processfor a general PDSCH reception. For example, in a general DL HARQprocess, the MAC entity may instruct a lower layer (e.g., a PHY layer)to generate acknowledgement(s) (e.g., an ACK or NACK) for the receivedTB based on whether the data in the received TB was successfully decodedor not. That is, the MAC entity instructs the PHY layer to perform theHARQ-ACK feedback based on whether the data in the received TB wassuccessfully decoded or not. However, the specific HARQ process inaction 746 may include, but is not limited to, one or more or anycombination of the following:

Implementation A:

As shown in FIG. 8 , the MAC entity may perform a specificaction/behavior. As illustrated in flowchart 800, action 852 includesreceiving a MSGB indicated by a DL assignment received on a PDCCH for aMSGB-RNTI (or a specific RNTI). Action 854 includes determining that theMSGB includes a success RAR (or a specific type of RAR). Action 856includes successfully performing contention resolution based on thesuccess RAR. Action 858 includes instructing a lower layer to generatean acknowledgement(s). For example, the MAC entity evaluates whether toinstruct a lower layer (e.g., the PHY layer) to generate anacknowledgement(s) (e.g., either a ACK or NACK)) for the received TB (asuccess RAR, a fallback RAR, a subPDU of a success RAR, a subPDU of afallback RAR, or a specific subPDU containing a MAC SDU as introduced inaction 218 in FIG. 2 ) based on one or more of the following:

-   -   whether the TB is indicated by a downlink assignment received on        PDCCH for specific RNTI (e.g., MSGB-RNTI/C-RNTI/UE specific        RNTI);    -   the content in the received TB;    -   the payload of the PDSCH in the received TB;    -   the MAC PDU carried by the PDSCH in the received TB;    -   the MAC subPDU carried by the PDSCH in the received TB;    -   the subheader of MAC subPDU carried by the PDSCH in the received        TB;    -   a specific field (e.g., LCID field) within the subheader of MAC        subPDU carried by the PDSCH in the received TB;    -   the SDU of MAC subPDU carried by the PDSCH in the received TB;    -   one more field (e.g., the Contention Resolution Identity) within        the SDU of MAC subPDU carried by the PDSCH in the received TB;        or    -   whether the corresponding contention resolution is successful.        Wherein the contention resolution success may be the Contention        Resolution Identity within the SDU of MAC subPDU carried by the        PDSCH in the received TB match one or more the following:        -   the content transmitted in MSGA;        -   the content of subPDU of the MAC PDU transmitted in the            MSGA; or        -   the content of SDU of the subPDU of the MAC PDU transmitted            in the MSGA.

Implementation B:

In the present implementation, similar as Implementation A above, thespecific behavior is replaced by “the MAC entity evaluates whether toinstruct a lower layer (e.g., a PHY layer) a specific situation”, wherethe specific situation may be, but is not limited to, the MAC entityhaving received/identified specific data. The specific data may include,but is not limited to, one or more of the following:

-   -   a success RAR (as shown in FIG. 5 );    -   a fallback RAR (as shown in FIG. 5 );    -   a success RAR (as shown in FIG. 5 ) indicated by a success RAR        specific LCID;    -   a success RAR indicated by a specific field as addressed in        action 218 in FIG. 2 ;    -   a fallback RAR (as shown in FIG. 5 ) indicated by a fallback RAR        specific LCID;    -   a fallback RAR indicated by a specific field as addressed in        action 218 in FIG. 2 ;    -   a success RAR which includes content of a C-RNTI;    -   a fallback RAR which includes content of a TC-RNTI; and/or    -   a success RAR which includes content of a contention resolution        ID (as shown in FIG. 5 ) match:        -   the content transmitted in a MSGA;        -   the content of a subPDU of a MAC PDU transmitted in a MSGA;            or        -   the content of a SDU of a subPDU of a MAC PDU transmitted in            a MSGA.

Implementation C:

In addition to the implementations A and B above, the presentimplementation includes additional conditions, for example, the specificaction/behavior may be performed only when the RA is triggered for aparticular purpose (e.g., a beam failure recovery, a system informationrequest or an RRC connection resume request, small data transmission).

Implementation D:

In the present implementation, after action 856 of FIG. 8 , the MACentity may further perform demultiplexing and disassembling of thesubPDU containing data for the SRB or DRB of the UE of which thecontention resolution is successful.

It should be noted that the specific actions/behaviors above may beperformed by (but are not limited to) the HARQ entity of the servingcell which received the MSGB from the MAC entity of the UE.

Tables 1 and 2 below are two example text proposals according to theImplementations A, B, C, and D above.

TABLE 1 Text Proposal for MAC Entity Once the MSGA is transmitted,regardless of the possible occurrence of a measurement gap, the MACentity shall:  1> start the msgB-ResponseWindow at the first PDCCHoccasion from the end of the MSGA transmission as specified in TS  38.213;  1> monitor the PDCCH of the SpCell for a random accessresponse identified by MSGB-RNTI while the msgB-   ResponseWindow isrunning;  1> if notification of a reception of a PDCCH transmission ofthe SpCell is received from lower layers:   2> if a downlink assignmenthas been received on the PDCCH for the MSGB-RNTI and the received TB issuccessfully    decoded:    3> if the MSGB contains a success RAR MACsubPDU; and    3> if the CCCH SDU was included in the MSGA and the UEContention Resolution Identity in the MAC subPDU     matches the CCCHSDU:     4> consider this Random Access Response reception successful;    4> consider this Random Access procedure successfully completed;    4> finish the disassembly and demultiplexing of the MAC PDU;     4>perform the specific behavior list in the embodiment b and/or e listedin section C;     4> instruct lower layer the received TB includes asuccess RAR MAC subPDU ;     4> instruct lower layer the MAC hasreceived a success RAR MAC subPDU corresponding to the transmitted     preamble;     4> instruct lower layer to generate acknowledgementfor the received TB;     4> instruct lower layer to generateacknowledgement for the success RAR MAC subPDU;     4> instruct lowerlayer to generate acknowledgement for the subPDU carrying (CCCH) SDU;    4> instruct lower layer the received TB includes a success RAR MACsubPDU and corresponding contention      resolution is success; and/or    4> instruct lower layer the contention resolution is success;

TABLE 2 Text Proposal for HARQ Entity      When a transmission takesplace for the HARQ process, one or two (in case of downlink spatialmultiplexing) TBs and the associated HARQ information are received fromthe HARQ entity.      For each received TB and associated HARQinformation, the HARQ process shall:  1> if the NDI, when provided, hasbeen toggled compared to the value of the previous received transmissioncorresponding to this TB; or  1> if the HARQ process is equal to thebroadcast process, and this is the first received transmission for theTB according to the system   information schedule indicated by RRC; or 1> if this is the very first received transmission for this TB (i.e.there is no previous NDI for this TB):   2> consider this transmissionto be a new transmission.  1> else:   2> consider this transmission tobe a retransmission.      The MAC entity then shall:  1> if this is anew transmission:   2> attempt to decode the received data.  1> else ifthis is a retransmission:   2> if the data for this TB has not yet beensuccessfully decoded:    3> instruct the physical layer to combine thereceived data with the data currently in the soft buffer for this TB andattempt to     decode the combined data.  1> if the data which the MACentity attempted to decode was successfully decoded for this TB; or  1>if the data for this TB was successfully decoded before:   2> if theHARQ process is equal to the broadcast process;    3> deliver thedecoded MAC PDU to upper layers.   2> else if this is the firstsuccessful decoding of the data for this TB:    3> deliver the decodedMAC PDU to the disassembly and demultiplexing entity.  1> else:   2>instruct the physical layer to replace the data in the soft buffer forthis TB with the data which the MAC entity attempted to decode.       1> if the HARQ process is associated with a transmissionindicated with a MSGB-RNTI and the MAC PDU identified  by the MSGB-RNTIdoes not contains any success RAR MAC subPDU; or        1> if the HARQprocess is associated with a transmission indicated with a MSGB-RNTI,and the MAC PDU identified  by the MSGB-RNTI contains at least onesuccess RAR MAC subPDU(s), and the CCCH SDU was included in the MSGA,and the UE  Contention Resolution Identity in all success RAR MAC subPDUcontained in the MAC PDU identified by the MSGB-RNTI does not matches the CCCH SDU; or        1> if the HARQ process is associated with atransmission indicated with a MSGB-RNTI, and the MAC PDU identified  bythe MSGB-RNTI contains success RAR MAC subPDU, and Contention Resolutionfor the random access of the MSGA transmission  identified by theMSGB-RNTI is not yet successful; or        1> if the HARQ process isassociated with a transmission indicated with a MSGB-RNTI for 2-step RAand  corresponding Contention Resolution is nor yet successful; or  1>if the HARQ process is associated with a transmission indicated with aTemporary C-RNTI and the Contention Resolution is not yet   successful(see clause 5.1.5); or  1> if the HARQ process is equal to the broadcastprocess; or  1> if the timeAlignmentTimer, associated with the TAGcontaining the Serving Cell on which the HARQ feedback is to betransmitted, is   stopped or expired:   2> not instruct the physicallayer to generate acknowledgement(s) of the data in this TB.  1 > else:  2> Instruct the physical layer to generate acknowledgement(s) of thedata in this TB:      2> Instruct the physical layer to generateacknowledgement(s) of the success RAR in this TB;   2> Instruct physicallayer to generate acknowledgement for the success RAR MAC subPDU in thisTB; and/or   2> Instruct physical layer to generate acknowledgement forthe subPDU carrying (CCCH) SDU in this TB

It should be noted that the MSGB-RNTI mentioned in Table 2 is theMSGB-RNTI determined/calculated by the UE according to the MSGAtransmission of the 2-step RA procedure.

IV. HARQ Feedback of MSGB Reception

In an NR wireless communication system, a DL data reception at the UEside is achieved by monitoring a PDCCH and finding possible DLassignment on the PDCCH. The assignment is represented as UE specificDCI, which may be found on a PDCCH (candidate). The DCI may indicate aDL data reception on a PDSCH. The DCI may also indicate the DL datacorresponding to a HARQ feedback (e.g., HARQ-ACK) related instruction.That is, the DCI indicates time and frequency locations of the PDSCH andindicates the timing at which the UE should perform the correspondingHARQ-ACK transmission.

Two parameters K0 and K1 were introduced in NR Release 15 as shown inFIG. 9 for PDSCH scheduling and the corresponding HARQ-ACK feedback. TheK0 is defined as a slot offset between a slot containing a PDCCHcarrying the DCI (i.e., the DCI indicates a following PDSCH reception)and a slot containing the PDSCH indicated (e.g., scheduled) by the DCI.The K1 is defined as a slot offset between the slot containing the PDSCHand the slot the UE needs to perform the HARQ-ACK feedback. DCI mayindicate what values of the K0 and K1 should be adopted by the UE whileperforming a PDSCH reception procedure. It should be noted that FIG. 9assumes that each subframe contains two slots (e.g., slot indices 0 and1). It should be noted that the number of slots contained within each ofsubframes is dependent on the numerology of numerology configuration.

As mentioned in description of action 214 in FIG. 2 , it is possiblethat a base station may transmit multiple random access responses (e.g.,a success RAR and/or a fallback RAR) within a single MSGB. That is, asingle MSGB may be received and be HARQ decoded by multiple UEsmonitoring the MSGB with same MSGB-RNTI. However, it is also possiblethat the MSBG may not contain a success RAR (corresponding to their MSGAtransmission) for each of the UEs. It is also possible that not all UEscan successfully pass at contention resolution (procedure) by thereceived MSGB. Only the MAC entity of the UE that is successful in thecontention resolution (e.g., receiving the success RAR corresponding totheir transmitted MSGA) may instruct their PHY layer to perform the HARQfeedback. However, it is a challenge for a base station to schedule(indicate) a proper K₁ and/or uplink radio resource (PUSCH/PUCCHresource), within the MSGB (e.g., a single MSGB), for the multiple UEsthat are successful in contention resolution by the MSGB.

As illustrated in FIG. 10 , DCI with CRC bits scrambled by an MSGB-RNTItransmitted on a PDCCH, by a base station, indicates a MSGB reception ona PDSCH. The MSGB contains two success RARs: Success RAR₁ and SuccessRAR₂. For example, the Success RAR₁ and Success RAR₂ are random accessresponse for UEs that transmitted preamble₁ and preamble₂, respectively.In the present example, it is assumed that the preamble₁ and preamble₂are selected and transmitted by the UE₁ (in MSGA₁) and UE₂ (in MSGA₂),respectively. That is, both the UE₁ and UE₂ are successful in contentionresolutions after receiving the MSGB (e.g., same MSGB).

The UL radio resource for the HARQ-ACK feedback of the Success RAR₁ andSuccess RAR₂ may at least include two pieces of information. The firstpiece of information is timing information (e.g., time interval). Thesecond piece of information may be one or more indicators indicating aUL radio resource among multiple UL radio resources located at thetiming indicated by the first piece of information.

The timing or time interval of the first piece of information may be,but is not limited to, time interval between the MSGB reception and theHARQ-ACK feedback (e.g., K₁). The time interval of the first piece ofinformation may be, but is not limited to, a value with the unit ofsymbol, sub-slot, slot, or sub-frame. For example, the first piece ofinformation indicates a slot offset between a first slot of MSGBreception and a second slot of the HARQ-ACK feedback. Also, the timeinterval of the second piece of information may be, but is not limitedto, a value with the unit of symbol, sub-slot, slot, or sub-frame. In anexample, the second piece of information indicates an uplink resourcefor the HARQ-ACK feedback transmission within the second slot. Thesecond piece of information indicates an uplink resource among multipleUL radio resources located within the second slot. In one example, themultiple UL radio resources located within the second slot arepreconfigured by RRC configuration. In one example, the UL radioresource is represented in a value with the unit of symbol. Theindicator mentioned in the second piece of information may at leastinclude one or more of the following:

-   -   PDCCH_resource_indicator: an indicator indicating which resource        should be applied (for HARQ-ACK feedback) by the UE among a list        of resource preconfigured by RRC or by a specific IE contained        in broadcast system information (e.g., system information block        (SIB) 1) received from gNB. For example, the specific IE may be,        but is not limited to, ServingCellConfigCommonSIB,        UplinkConfigCommonSIB, BWP-UplinkCommon and/or        pusch-ConfigCommon. For example, the PUCCH_resource_indicator        indicates an uplink resource for the HARQ-ACK feedback        transmission within the second slot. The        PUCCH_resource_indicator indicates an uplink resource among        multiple UL radio resources located within the second slot. In        one example, the multiple UL radio resources located within the        second slot are preconfigured by RRC configuration. In one        example, the UL radio resource is represented in a value with        the unit of symbol.    -   PUCCH_resource_offset: an indicator indicating an offset. The        offset may be applied by the UE to find out which resource        should be applied (for HARQ-ACK feedback) among a list of        resource preconfigured by RRC or by a specific IE contained in        broadcast system information (e.g., system information block        (SIB) 1) received from gNB. For example, the specific IE may be,        but is not limited to, ServingCellConfigCommonSIB,        UplinkConfigCommonSIB, BWP-UplinkCommon and/or        pusch-ConfigCommon. For example, the UE should apply the x^(th)        entry of within the list of resource preconfigured by RRC.        Wherein, the x may be (but is not limited to) calculated by the        UE as: the x=y+PUCCH_resource_offset. And the y is the entry        indicated by the PUCCH_resource_indicator. In another        embodiment, the PUCCH_resource_offset indicating offset in        frequency and/or time domain and/or resource block (i.e.,        physical layer resource unit) indexing. The resource for        HARQ-feedback is determined by PUCCH resource indicated by the        PUCCH_resource_indicator and the offset.

As illustrated in FIG. 10 , the base station may transmit the firstand/or second pieces of information to the UE in on or more of thefollowing:

-   -   (a) in one or more fields within the DCI;    -   (b) by setting one or multiple fields within the DCI as a        pre-defined value;    -   (c) in one or more fields within each subheader of success RAR        (e.g., Subheader₁ and Subheader₂);    -   (d) in one or more fields within the RAR SDU₁ and RAR SDU₂        (e.g., success RAR₁ and success RAR₂);    -   (e) implicitly represented by the order of the subPDU containing        the success RAR within the MAC PDU of the MSGB. For example, the        success RAR₁ is placed in the first order of all success RARs,        then the indicator was implicitly represented as indicating a        value 1. For example, the success RAR₂ is placed in the second        order of all success RARs, and then the indicator was implicitly        represented as indicating a value 2.

Based on the (c), (d) and (e) introduced as above, FIG. 11 illustratesan example flowchart of a method of handling, by the MAC entity and PHYlayer, MSGB reception, contention resolution and HARQ-ACK feedback.

As shown in action 1168 of flowchart 1100, after the contentionresolution is successful in action 1166, the MAC/HARQ entity may deliverspecific assist information to the PHY layer for assisting the PHY layerto determine a PUCCH resource for a HARQ-feedback of the success RAR.Afterward, in action 1170 the MAC/HARQ entity may further instruct thePHY layer to generate an acknowledgement. In one example, actions 1168and 1170 of flowchart 1100 may be performed immediately after theMAC/HARQ entity determines the MSGB contains a success RAR. In anotherexample, actions 1168 and 1170 of flowchart 1100 may be performedimmediately after the MAC/HARQ entity determines the MSGB contains asuccess RAR and before the contention resolution success.

Tables 3, 4, and 5 below are three example text proposals according tothe HARQ feedback of MSGB reception implementations descried above.

TABLE 3 Text Proposal for MAC Entity Once the MSGA is transmitted,regardless of the possible occurrence of a measurement gap, the MACentity shall:  1> start the msgB-ResponseWindow at the first PDCCHoccasion from the end of the MSGA transmission as specified in TS38.213;  1> monitor the PDCCH of the SpCell for a random access responseidentified by MSGB-RNTI while the msgB-ResponseWindow is running;  1> ifnotification of a reception of a PDCCH transmission of the SpCell isreceived from lower layers:   2> if a downlink assignment has beenreceived on the PDCCH for the MSGB-RNTI and the received TB issuccessfully decoded:    3> if the MSGB contains a success RAR MACsubPDU; and     4> deliver the specific assist information to lowerlayer;    3> if the CCCH SDU was included in the MSGA and the UEContention Resolution Identity in the MAC subPDU matches the     CCCHSDU:     4> consider this Random Access Response reception successful;    4> consider this Random Access procedure successfully completed;    4> finish the disassembly and demultiplexing of the MAC PDU.

TABLE 4 Text Proposal for MAC Entity Once the MSGA is transmitted,regardless of the possible occurrence of a measurement gap, the MACentity shall:  1> start the msgB-ResponseWindow at the first PDCCHoccasion from the end of the MSGA transmission as specified in TS38.213;  1> monitor the PDCCH of the SpCell for a random access responseidentified by MSGB-RNTI while the msgB-ResponseWindow is running;  1> ifnotification of a reception of a PDCCH transmission of the SpCell isreceived from lower layers:   2> if a downlink assignment has beenreceived on the PDCCH for the MSGB-RNTI and the received TB issuccessfully decoded:    3> if the MSGB contains a success RAR MACsubPDU; and     3> if the CCCH SDU was included in the MSGA and the UEContention Resolution Identity in the MAC subPDU matches the      CCCHSDU:      4> consider this Random Access Response reception successful;     4> consider this Random Access procedure successfully completed;     4> finish the disassembly and demultiplexing of the MAC PDU.     4> deliver the specific assist information to lower layer;

TABLE 5 Text Proposal for HARQ Entity      When a transmission takesplace for the HARQ process, one or two (in case of downlink spatialmultiplexing) TBs and the associated HARQ information are received fromthe HARQ entity.      For each received TB and associated HARQinformation, the HARQ process shall:  1> if the NDI, when provided, hasbeen toggled compared to the value of the previous received transmissioncorresponding to this TB; or  1> if the HARQ process is equal to thebroadcast process, and this is the first received transmission for theTB according to the system   information schedule indicated by RRC; or 1> if this is the very first received transmission for this TB (i.e.there is no previous NDI for this TB);   2> consider this transmissionto be a new transmission.  1> else:   2> consider this transmission tobe a retransmission.      The MAC entity then shall:  1> if this is anew transmission:   2> attempt to decode the received data.  1> else ifthis is a retransmission:   2> if the data for this TB has not yet beensuccessfully decoded:    3> instruct the physical layer to combine thereceived data with the data currently in the soft buffer for this TB andattempt to     decode the combined data.  1> if the data which the MACentity attempted to decode was successfully decoded for this TB; or  1>if the data for this TB was successfully decoded before:   2> if theHARQ process is equal to the broadcast process:    3> deliver thedecoded MAC PDU to upper layers.   2> else if this is the firstsuccessful decoding of the data for this TB:    3> deliver the decodedMAC PDU to the disassembly and demultiplexing entity.  1> else:   2>instruct the physical layer to replace the data in the soft buffer forthis TB with the data which the MAC entity attempted to decode.  1> ifthe HARQ process is associated with a transmission indicated with aC-RNTI for 2-step RA and corresponding Contention Resolution   is notyet successful; or  1> if the HARQ process is associated with atransmission indicated with a Temporary C-RNTI and the ContentionResolution is not yet   successful (see clause 5.1.5); or  1> if theHARQ process is equal to the broadcast process; or  1> if thetimeAlignmentTimer, associated with the TAG containing the Serving Cellon which the HARQ feedback is to be transmitted, is   stopped orexpired:   2> not instruct the physical layer to generateacknowledgements) of the data in this TB.  1> else:   2> Instruct thephysical layer to generate acknowledgement(s) of the data in this TB; or      2> deliver the specific assist information to lower layer;

FIG. 12 illustrates a flowchart 1200 of a method by a UE for performinga random access procedure in accordance with an example implementationof the present disclosure. As illustrated in flowchart 1200, action 1282may include receiving, by reception circuitry of the UE, a list of PUCCHresource offset candidates each indicating a timing offset, the list ofPUCCH resource offset candidates being associated with a UL BWP.

Action 1282 may include transmitting, by transmit circuitry, a MSGA of a2-step random access procedure. In one implementation, the MSGA containsa CCCH SDU.

Action 1284 may include monitoring a MSGB-RNTI within a MSGB window, theMSGB window starting from an earliest symbol (e.g., a first symbol) ofan earliest PDCCH occasion (e.g., a first PDCCH occasion) after an endof the MSGA transmission.

Action 1286 may include receiving, by reception circuitry, the MSGB in afirst slot in response to the MSGA, the MSGB including a success RAR,the success RAR containing a HARQ Feedback Timing Indicator, a PUCCHResource Indicator, and a UE Contention Resolution Identity.

Action 1288 may include determining, by a MAC entity, to instruct alower layer (e.g., a PHY layer) to transmit a HARQ feedback in a secondslot in response to the reception of the success RAR, the second slotindicated by the HARQ Feedback Timing Indicator. In one implementation,the second slot is offset from the first slot by one of the timingoffsets determined by the list of PUCCH resource offset candidates.

Action 1290 may include delivering, by the MAC entity of the UE, theHARQ Feedback Timing Indicator and the PUCCH Resource Indicator to thelower layer.

Action 1292 may include performing, by the lower layer, a HARQ feedbackdelivery on a UL resource within the second slot determined by the HARQFeedback Timing Indicator and the PUCCH Resource Indicator. In oneimplementation, the HARQ feedback is delivered when the UE ContentionResolution Identity in a MAC sub-PDU matches the CCCH SDU. In oneimplementation, the HARQ feedback is transmitted on the UL BWP.

FIG. 13 illustrates a block diagram of a node for wirelesscommunication, in accordance with various aspects of the presentdisclosure. As illustrated in FIG. 13 , the node 1300 may include atransceiver 1306, a processor 1308, a memory 1302, one or morepresentation components 1304, and at least one antenna 1310. The node1300 may also include an RF spectrum band module, a BS communicationsmodule, a network communications module, and a system communicationsmanagement module, Input/Output (I/O) ports, I/O components, and a powersupply (not explicitly illustrated in FIG. 13 ). Each of thesecomponents may be in communication with each other, directly orindirectly, over one or more buses 1324. In one implementation, the node1300 may be a UE or a BS that performs various functions disclosedherein, for example, with reference to FIGS. 1 through 10 .

The transceiver 1306 having a transmitter 1316 (e.g.,transmitting/transmission circuitry) and a receiver 1318 (e.g.,receiving/reception circuitry) may be configured to transmit and/orreceive time and/or frequency resource partitioning information. In oneimplementation, the transceiver 1306 may be configured to transmit indifferent types of subframes and slots, including, but are not limitedto, usable, non-usable, and flexibly usable subframes and slot formats.The transceiver 1306 may be configured to receive data and controlchannels.

The node 1300 may include a variety of computer-readable media.Computer-readable media can be any available media that can be accessedby the node 1300 and include both volatile (and non-volatile) media andremovable (and non-removable) media. By way of example, and notlimitation, computer-readable media may include computer storage mediaand communication media. Computer storage media may include bothvolatile (and/or non-volatile) and removable (and/or non-removable)media implemented according to any method or technology for storage ofinformation such as computer-readable instructions, data structures,program modules or data.

Computer storage media may include RAM, ROM, EPROM, EEPROM, flash memory(or other memory technology), CD-ROM, Digital Versatile Disks (DVD) (orother optical disk storage), magnetic cassettes, magnetic tape, magneticdisk storage (or other magnetic storage devices), etc. Computer storagemedia do not include a propagated data signal. Communication media maytypically embody computer-readable instructions, data structures,program modules, or other data in a modulated data signal such as acarrier wave or other transport mechanisms and include any informationdelivery media. The term “modulated data signal” may mean a signal thathas one or more of its characteristics set or changed in such a manneras to encode information in the signal. By way of example, and notlimitation, communication media may include wired media such as a wirednetwork or direct-wired connection, and wireless media such as acoustic,RF, infrared, and other wireless media. Combinations of any of the aboveshould also be included within the scope of computer-readable media.

The memory 1302 may include computer storage media in the form ofvolatile and/or non-volatile memory. The memory 1302 may be removable,non-removable, or a combination thereof. For example, the memory 1302may include solid-state memory, hard drives, optical-disc drives, etc.As illustrated in FIG. 13 , the memory 1302 may store computer-readableand/or computer-executable instructions 1314 (e.g., software codes) thatare configured to, when executed, cause the processor 1308 to performvarious functions disclosed herein, for example, with reference to FIGS.1 through 10 . Alternatively, the instructions 1314 may not be directlyexecutable by the processor 1308 but may be configured to cause the node1300 (e.g., when compiled and executed) to perform various functionsdisclosed herein.

The processor 1308 (e.g., having processing circuitry) may include anintelligent hardware device, a Central Processing Unit (CPU), amicrocontroller, an ASIC, etc. The processor 1308 may include memory.The processor 1308 may process the data 1312 and the instructions 1314received from the memory 1302, and information through the transceiver1306, the baseband communications module, and/or the networkcommunications module. The processor 1308 may also process informationto be sent to the transceiver 1306 for transmission through the antenna1310, to the network communications module for transmission to a CN.

One or more presentation components 1304 may present data indications toa person or other devices. Examples of presentation components 1304 mayinclude a display device, speaker, printing component, vibratingcomponent, etc.

From the present disclosure, it is manifested that various techniquesmay be used for implementing the disclosed concepts without departingfrom the scope of those concepts. Moreover, while the concepts have beendisclosed with specific reference to certain implementations, a personof ordinary skill in the art would recognize that changes may be made inform and detail without departing from the scope of those concepts. Assuch, the disclosed implementations are to be considered in all respectsas illustrative and not restrictive. It should also be understood thatthe present disclosure is not limited to the particular disclosedimplementations. Still, many rearrangements, modifications, andsubstitutions are possible without departing from the scope of thepresent disclosure.

What is claimed is:
 1. A method performed by a user equipment (UE) for a2-step random access (RA) procedure including a message A (MSGA) and amessage B (MSGB), the method comprising: transmitting the MSGA of the2-step RA procedure, the MSGA including a Common Control Channel (CCCH)Media Access Control (MAC) Service Data Unit (SDU); monitoring anMSGB-Radio Network Temporary Identity (RNTI) within an MSGB time window,the MSGB time window starting from an earliest symbol of an earliestPhysical Downlink Control Channel (PDCCH) occasion after an end of theMSGA transmission; receiving, in response to transmitting the MSGA, theMSGB in a first slot, the MSGB including a success random accessresponse (RAR), the success RAR containing a Hybrid Automatic RepeatreQuest (HARQ) Feedback Timing Indicator, a Physical Uplink ControlChannel (PUCCH) Resource Indicator, and a UE Contention ResolutionIdentity; determining, by a MAC entity of the UE, to instruct a lowerlayer to transmit a HARQ feedback in response to the reception of thesuccess RAR, wherein: the HARQ feedback is transmitted in a second slotdetermined by the HARQ Feedback Timing Indicator, and the second slot isseparated from the first slot by an offset, the offset comprising atiming offset value determined from a list of PUCCH resource offsetcandidates; delivering, by the MAC entity of the UE, the HARQ FeedbackTiming Indicator and the PUCCH Resource Indicator to the lower layer;and transmitting, by the lower layer, the HARQ feedback on an uplink(UL) resource within the second slot in response to the UE ContentionResolution Identity in a MAC sub-Protocol Data Unit (subPDU) of thesuccess RAR matching the CCCH MAC SDU, wherein: the UL resource isdetermined by the PUCCH Resource Indicator and corresponds to one of thelist of PUCCH resource candidates indicated by the PUCCH ResourceIndicator, and the list of PUCCH resource candidates is associated witha UL bandwidth part (BWP).
 2. The method of claim 1, wherein the HARQfeedback is transmitted on the UL BWP.
 3. The method of claim 1, whereinthe list of PUCCH resource candidates is preconfigured by a radioresource control (RRC) configuration.
 4. The method of claim 1, whereinthe lower layer comprises a physical (PHY) layer of the UE.
 5. A userequipment (UE) configured to perform a 2-step random access (RA)procedure including a message A (MSGA) and a message B (MSGB), the UEcomprising: one or more non-transitory computer-readable media storingone or more computer-executable instructions; and at least one processorcoupled to the one or more non-transitory computer-readable media, andconfigured to execute the one or more computer-executable instructionsto cause the UE to: transmit the MSGA of the 2-step RA procedure, theMSGA including a Common Control Channel (CCCH) Media Access Control(MAC) Service Data Unit (SDU); monitor an MSGB-Radio Network TemporaryIdentity (RNTI) within an MSGB time window, the MSGB time windowstarting from an earliest symbol of an earliest Physical DownlinkControl Channel (PDCCH) occasion after an end of the MSGA transmission;receive, in response to transmitting the MSGA, the MSGB in a first slot,the MSGB including a success random access response (RAR), the successRAR containing a Hybrid Automatic Repeat reQuest (HARQ) Feedback TimingIndicator, a Physical Uplink Control Channel (PUCCH) Resource Indicator,and a UE Contention Resolution Identity; determine, by a MAC entity ofthe UE, to instruct a lower layer to transmit a HARQ feedback inresponse to the reception of the success RAR, wherein: the HARQ feedbackis transmitted in a second slot determined by the HARQ Feedback TimingIndicator, and the second slot is separated from the first slot by anoffset, the offset comprising a timing offset value determined from alist of PUCCH resource offset candidates; deliver, by the MAC entity ofthe UE, the HARQ Feedback Timing Indicator and the PUCCH ResourceIndicator to the lower layer; and transmit, by the lower layer, the HARQfeedback on an uplink (UL) resource within the second slot, the ULresource being determined by the PUCCH Resource Indicator when the UEContention Resolution Identity in a MAC sub-Protocol Data Unit (subPDU)of the success RAR matches the CCCH MAC SDU, the UL resourcecorresponding to one of the list of PUCCH resource candidates indicatedby the PUCCH Resource Indicator, wherein the list of PUCCH resourcecandidates is associated with a UL bandwidth part (BWP).
 6. The UE ofclaim 5, wherein the HARQ feedback is transmitted on the UL BWP.
 7. TheUE of claim 5, wherein the list of PUCCH resource candidates ispreconfigured by a radio resource control (RRC) configuration.
 8. The UEof claim 5, wherein the lower layer comprises a physical (PHY) layer ofthe UE.